Note
that the appearance of the retina varies with location. The concentration
of cells (and resulting thickness of the retina)
decreases toward the periphery (i.e., with increasing distance from the
macula).

Retinal layers

The green line at the top of the
image (above the nerve fiber layer) is the site of the inner limiting
membrane, a basal lamina separating nervous tissue of the retina
from connective tissue of the vitreous
humor.

The
layer of nerve fibers contains axons from ganglion
cells which travel across the retina to the optic
nerve and hence past the optic chiasm into the optic tract and into
lateral geniculate nucleus of the thalamus.

The ganglion cell layer contains the cell bodies of ganglion
cells, the cells whose axons project to the brain.

The pigmented epithelium absorbs light not captured by photoreceptors,
and also contributes to the maintenance of rods and cone outer segments.

The red line between the outer nuclear
layer and the receptor layer is the site of the outer limiting membrane,
a basal lamina bounding the neural retina. The outer segments (rods
and cones) of the receptor cells penetrate the outer membrane to contact
the pigmented epithelium.

The optic vesicle itself collapses into a cup. The front surface
of this vesicle (the hollow of the cup) becomes the neural retina,
while the back surface becomes the retina's pigmented epithelium.

Although cells of the pigmented
epithelium are intimately associated with outer segments (rods and
cones) of receptor cells, this surface where the neural retina
contacts the pigmented epithelium
is inherently extremely fragile and is the site where retinal detachment
can occur.